Controversy: Are Green Smoothies Unhealthy?

If you are reading this, you probably already know about green smoothies and the many health benefits they provide.

However, every couple of months, somebody writes a terrifying article exposing the impending “health disaster” that is the green smoothie.

Uh oh! Green smoothies will devastate your health…or so they say.

And every time one of these articles appear on the Internet, I get bombarded with questions from people who are scared to death to put their lips to a glass of green smoothie (again).

Are there any side effects to drinking a daily green smoothie?

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Are there certain people who should not drink green smoothies?

Do green smoothies have a dark side?

Let’s tackle the most common green smoothie controversies.

You can skip to a specific topic by choosing any of the links below.

I’ve also included a TL;DR summary in case this epic article is more nutritional geekery than you have time to dive into right now.

  1. Do Green Smoothies Contain Too Much Sugar?
  2. Will Green Smoothies Cause Weight Gain?
  3. Aren’t Green Smoothies Too High In Carbohydrates?
  4. Should I Make Green Smoothies With Less Fruit And More Greens?
  5. Do Green Smoothies Increase Diabetes Risk?
  6. Will The Fruit Sugars In Green Smoothies Rot Your Teeth?
  7. Will Raw Kale Destroy My Thyroid?
  8. Is The Oxalic Acid (Oxalate) Content Of Raw Spinach Bad For Me?
  9. Does Blending Destroy 90% Of The Nutrients In My Smoothies? What About The Fiber?
  10. Isn’t It Improper Food Combining To Mix Greens/Vegetables With Fruit?
  11. Blending vs. Chewing: Which Is The Better Way?

1) Do Green Smoothies Contain Too Much Sugar?

As a blend of sweet fruits and leafy greens, the majority of the calories in green smoothies come from carbohydrates – particularly sweet fruits. Since sweet fruit is high in sugars, is a daily green smoothie or two providing too much sugar in your diet?

I have looked into this issue extensively, and the bottom line is this:

1) Naturally-occurring sugars (like the ones found in fruit) do not cause the health problems associated with added sugars (like the ones found in soft drinks and baked goods).

2) Scientifically established sugar intake guidelines published by the World Health Organization (WHO), American Heart Association (AHA), and The National Institute of Medicine are for added sugars only, and specifically state that naturally-occurring sugars are not a health concern.

3) There is zero evidence that fruit, or the sugars in fruit, cause weight gain, or increase one’s risk for developing type 2 diabetes. In fact, the overwhelming body of medical studies suggest that diets higher in fruits and vegetables have lower risk for obesity and diabetes.

You don’t even have to avoid “high glycemic” fruits like bananas and watermelon, either. Read more about Glycemic Index vs. Glycemic Load.

TL;DR: The naturally-occurring sugars in green smoothies are not a health risk, unless you have a medical need (such as diabetes) to restrict carbs from all sources.


2) Will Green Smoothies Cause Weight Gain?

I lost 40 pounds with green smoothies and a plant-based, whole foods diet.

In the 8 years that I have had my blog, I have read thousands upon thousands of weight loss testimonials attributed to green smoothies.

It truly surprises me that there is even a controversy about using green smoothies for weight loss.

I will tackle some of the more specific weight loss-related controversies below.

Calorie Reduction Controversy: The most recent exposé about the “unhealthiness” of green smoothies cites this health study comparing the satiety of different forms of fruit (whole apple, apple sauce, apple juice and apple juice with fiber added) and how it affects total calorie intake.

The study found that eating a whole apple reduced calorie intake of the following meal by 15% while consuming apple sauce decreased calorie intake by 6% in the following meal. Drinking apple juice with fiber reduced calorie consumption of a meal by only 1% while straight up apple juice actually increased calorie intake by 3%.

Assumptions based on the data presented by this study suggests that eating whole fruits promotes a significant decrease in calorie consumption while pureed fruit is not as effective at reducing overall calorie intake. However, there is a big difference between a freshly blended green smoothie and cooked apple sauce. You can’t even compare the two as they contain different foods and are processed in completely different ways.

Furthermore, the conclusion of the study explicitly states that “more research is needed to test the effects of consuming different forms of fruit on energy intake over longer periods of time before conclusions about the role of fruit in different forms in weight management can be made.”

While it makes sense that consuming apple sauce may not be as satisfying, a green smoothie – especially when it is consumed as a meal – is filling and results in lower caloric intake overall.

A calorie-sufficient green smoothie MEAL will satisfy your hunger until your next meal and reduce overall calorie intake for the day – unless the rest of your diet isn’t healthy.

Excess Calories From Green Smoothies Because You Are Not Chewing Them: I recently read an argument stating that drinking green smoothies could add up to 100 excess calories per meal because chewing burns calories, where drinking does not. Therefore, eating your greens in a salad is better for weight loss than drinking your greens in a smoothie.

I’m not sure how they got the idea that chewing a meal consumes 100 calories. My calculations are closer to 27 calories consumed by chewing for a solid hour. In the grand scheme of things, burning 27 calories while chewing (for an hour, mind you) is not going to make or break your weight loss success.

If anything, you’ll burn more calories with green smoothies because they will be efficiently digested and provide more energy to exercise and live an active lifestyle. And you are more likely to stick with it. It’s much easier and way more convenient to drink a green smoothie every day than it is to eat a giant bowl of salad.

TL;DR: Tons of anecdotal evidence (and my own personal experience) points to green smoothies as a significant booster to weight loss by naturally reducing overall calories, increasing fiber, and boost nutrients. The carbs, sugars, calories in a typical green smoothie does not directly contribute to weight gain. Look to other areas of diet and lifestyle.


3) Aren’t Green Smoothies Too High In Carbohydrates?

A common question I get about green smoothies is regarding their carbohydrate content. A typical green smoothie meal may have excess of 50+ carbs.

Is that a bad thing? Will that make you fat? Will it increase your risk for diabetes?

Good Carbs vs. Bad Carbs: You have probably heard about “good carbohydrates” and “bad carbohydrates”. Not all carbs are created equal. There’s no argument that donuts, pasta, white rice (and bread), soda and sweetened beverages, cookies, and cupcakes are all bad carbohydrates. These foods are at the forefront of the obesity epidemic.

However, fresh, whole, ripe fruits are in a completely different league than pastries. It’s a tragedy that so many people (including some doctors) lump them in with the “foods that must go” when you are trying to lose weight.

Fruits, even sweet fruits like bananas, mangoes and grapes aren’t just made up of sugar or carbohydrates. They provide excellent sources of vitamins, minerals and antioxidants. They contain lots of fiber, which slows down digestion so that you don’t get hit with a sugar rush, like you would drinking a bottle of soda.

While it is good practice to limit added sugars, sweet fruits don’t count as added dietary sugar because they are whole foods. (If you are diabetic, however, you may still need to limit your intake of carbohydrates from all sources – including fruit.)

Carbs Don’t Make You Fat, Excess Calories Do: Excess calories, rather than carbohydrates, are the cause of weight gain. Calories provide energy for your body, but excess calories are stored as fat. It doesn’t matter if these calories come from pizza (high-carb) or prime rib (low-carb). There is nothing special about a banana that makes fat cling to your hips. It’s not the sugar or carbohydrate, it’s excess calories from your overall, daily eating habits.

Fundamentally, weight loss is about reducing total calorie intake to create a deficit, which forces your body to burn accumulated fat as fuel.

So it really doesn’t matter if you go on a low-carb diet or a high-carb diet, you still need to cut calories to an appropriate level to facilitate weight loss.

Low carb diets are often promoted for weight loss because most high-carbohydrate foods are unhealthy. They are loaded with added sugars, refined wheat flour, trans-fats. They don’t fill you up or satisfy you. They make it very easy to go overboard on calories. It’s easy to tell people to avoid carbs.

Fresh fruits (and green smoothies), on the other hand, contain no added sugars, fats, or refined ingredients. While a blueberry muffin the size of your fist might contain 600+ calories, it would take 60 ounces or more of a blueberry green smoothie to match that amount of calories. I bet you’d certainly feel it if you tried to drink that much!

A 32-ounce green smoothie meal replacement will help you feel full and satisfied. The sweet fruit will help curb your cravings for sweets (without all of the negative effects of added sugars). And you’ve only consumed about 350-400 calories for your breakfast (a great start).

TL;DR: No. Whole food carbohydrates behave differently in your body than carbs like pasta, white bread, white rice, cookies, and sweetened beverages.

There is not one single piece of medical evidence that suggests that consuming fruit or other whole food carbohydrates (quinoa, brown rice, whole grains), increase risk of obesity or disease. In fact, the evidence shows the opposite!


4) Should I Make Green Smoothies With Less Fruit And More Greens?

There is no need to restrict or limit sweet fruit in your green smoothies unless you have a medical reason to do so.

Are you diabetic? Check out low-carb green smoothie recipes!

In general, my green smoothies contain 60% fruit and 40% greens by volume.

My typical 32-ounce meal replacement green smoothie will contain about 300-400 calories (men will probably be more satisfied with a 500-calorie green smoothie – about 4 pieces of fruit – banana, mango, apple and orange) and an entire head of romaine lettuce (or four cups of other leafy green). Adding this much fruit provides the calories to make this smoothie a meal.

A vegetable-based smoothie will not provide sufficient calories to be a meal replacement smoothie. Even if you made a 32-ounce smoothie with just one apple, 1/2 cup blueberries, and a ton of vegetables and greens, you won’t come anywhere close to 400 calories. You’d be lucky to get 200 calories.

The problem with this is that you might still feel full from the fiber, but you risk under-consuming calories, especially if you follow a raw food or whole foods diet. Getting too few calories will sabotage weight loss and lead to nutrient deficiencies and health problems.

In short, fruit-based green smoothies can replace meals and are effective for weight loss. Plus, the 60:40 ratio (fruits to greens) is best for flavor, too.

Vegetable-based smoothies are too low in calories to be considered meals, so they are better used to supplement a calorie-sufficient whole foods diet between meals or consumed with meals – if you wish to do so.

TL;DR: Unless you are physically bothered by fruity green smoothies, I don’t think you need to worry about restricting fruit (or green smoothie intake).

If you are concerned about sugar, look into other areas of your diet first. Cut out all refined sweeteners, soda/pop, fruit juice, white rice and white bread. Green smoothies should replace unhealthy foods.


5) Do Green Smoothies Increase Diabetes Risk?

There is no evidence for this. In fact, the overwhelming evidence from decades of published health studies show that people who consume more fruits and vegetables have a lower risk of developing diabetes.

The etiology of diabetes is much more complex than “eat sugar, get diabetes”. There are often genetic, lifestyle, environmental, and dietary (not just sugar and carbs, but also fat) that play a role rather than a simple dietary faux pas.

The health studies that have pointed to sugar as a potential risk factor for diabetes specifically state that added sugars are the culprit (specifically sugar-sweetened beverages), and NOT the naturally-occurring sugars found in fruits and other whole foods.

TL;DR: No, there is no medical evidence that eating fruit or drinking green smoothies cause diabetes.


6) Will Drinking Green Smoothies Rot Your Teeth?

Sugars that are in the fruits that you blend in a green smoothie do come in contact with your teeth and feed the bacteria in your mouth that promote tooth decay. However, green smoothies are not the only source of sugars and even non- sugary foods like nuts can lead to dental problems.

It is important to good dental hygiene no matter what you eat. Fruit doesn’t rot your teeth, but poor dental hygiene or compromised health and lack of nutrients can lead to dental problems whether you eat “too much” fruit or not.

A major benefit from green smoothies is that you can increase your leafy green intake which will naturally boost the amount of calcium, magnesium and phosphorus in your diet – three minerals that help build and maintain strong bones.

TL;DR: You can drink green smoothies with a straw to minimize contact with teeth. However, proper dental hygiene is what prevents dental issues, not avoiding fruit and green smoothies.


7) Will Raw Kale Destroy My Thyroid

No, it will not. There isn’t any evidence that consuming a two handfuls of raw kale in a green smoothie every day will have any negative impact on thyroid function.

However, raw kale and other cruciferous vegetables like bok choy, broccoli, and cabbage, can exacerbate an existing thyroid condition. It may also interfere with thyroid medication.

If you have a thyroid disorder, it’s best to check in with your doctor or a dietitian to determine how much raw cruciferous vegetables are safe for you to consume.

If you have a healthy thyroid, then there is no need to worry about kale affecting it.

TL;DR: There is no evidence that consuming kale in green smoothies will cause thyroid disorder in healthy individuals.

Those with compromised thyroid function may need to restrict certain cruciferous vegetables.


8) Is The Oxalic Acid (Oxalate) Content Of Spinach Bad For Me?

Oxalic acid is a naturally occurring chemical in plants and animals. As such, it is consumed in a variety of different foods such as leafy greens, nuts, seeds, most berries, certain fruits, soy and soy products, meat, and dairy products.

In large amounts, oxalic acid is toxic. However, toxic levels are not found in foods that we typically eat.

The main controversy surrounding oxalic acid in food is whether or not they contribute to the formation of kidney stones.

About 80% of the kidney stones formed by adults in the U.S.A. are composed of calcium oxalate. Oxalic acid binds with other minerals such as calcium which form a salt known as an oxalate. Oxalic acid interferes with the absorption of calcium in foods by binding with the mineral, making it unusable by your body.

Without oxalic acid, foods such as spinach and kale would have a much higher, bio-available calcium content than they do because it is bound up with oxalic acid. These oxalates are usually passed though the urine but in vulnerable individuals, they may crystallize, forming larger stones that cause excruciating pain and require medical attention.

Many foods contain oxalic acid, especially leafy greens such as spinach, kale, chard, parsley, collards, and beet greens. Spinach has the highest levels of oxalic acid – 750 milligrams per 100 gram serving.

So, should you be concerned about the oxalate content of your spinach green smoothies?

Should You Be Concerned? The short answer is “generally, no”.

There are a few rare medical conditions such as Primary Hyperoxaluria and Enteric Hyperoxaluria where one would need to restrict their dietary intake of oxalic acid.

Also, those who are susceptible and have been treated for calcium-oxalate kidney stones, and therefore at risk of forming them again, should watch their intake of oxalate-containing foods.

Oxalic acid is not believed to be a health concern for most people. Keep in mind that your body regularly produces oxalic acid, often synthesizing other substances such as vitamin C into oxalic acid.

Whether you eat foods that contain it or not, your body maintains a naturally-occurring level of oxalic acid and regularly produces it whether you consume it in your diet or not.

The nutritional benefits of eating oxalate-containing foods such as spinach outweigh the minute risk of forming kidney stones. Plus, there isn’t any clinical evidence directly linking spinach consumption with the formation of kidney stones.

If You Are Concerned About Oxalates – If you have a history of kidney stones or a medical condition that is complicated by the consumption of oxalate-rich foods, you should contact your doctor or health practitioner for advice.

There is some helpful information on the web which lists oxalate levels of many foods which can help you plan your diet should you feel the need to reduce your intake of oxalic acid-containing foods.

TLDR: Naturally-occurring levels of oxalic acid in spinach is not a health concern, unless you currently have, have had, or are at risk for developing calcium-oxalate kidney stones.


9) Does Blending Destroy 90% Of The Nutrients In My Smoothies? What About The Fiber?

No, blending does not turn your nutritious fruit into junk food. There is absolutely no evidence that blending will reduce nutrient content by 90%.

Blending doesn’t destroy the fiber, either. Yes, blenders will break down fiber, but won’t strip out fiber like juicing does.


10) Isn’t It Improper Food Combining To Mix Greens/Vegetables With Fruit?

The food combining hypothesis was debunked more than 70 years ago, and is not consistent with what we now know about human digestion.

There is no scientific basis for abiding by food combining rules. There is nothing wrong with blending greens with fruit, or mixing acid fruits (citrus) with sweet fruits (bananas). Feel free to blend melons with anything you want in your green smoothies.


11) Blending vs. Chewing

I touched on this in the weight loss section earlier, but this is in regards to whether or not it is overall healthier to chew your food or drink it – specifically for digestion.

Chewing releases saliva and digestive enzymes. It’s the first step in the digestive process. However, that doesn’t mean that drinking a green smoothie will hinder proper digestion.

Saliva is still released as you drink a green smoothie. In fact, you’ll probably start salivating as you chop the ingredients and add them to your blender. I usually snack on bits of fruit and even greens as I make my smoothie. This helps rev up the digestive engine.

Each sip you take ads saliva. And your stomach and intestines are perfectly capable of digesting it.

Some people are concerned that drinking green smoothies can cause the jaw to atrophy and weaken. I find this fear to be totally unfounded. Your jaw is not going to atrophy by drinking one or two green smoothies per day.

As far as digestion is concerned, green smoothies are very easy to digest because they’ve been thoroughly blended (or mechanically chewed, you could say). If anything, a blended smoothie will digest more efficiently than chewed whole fruits. It’s still entering your mouth, mixing with saliva, and entering your stomach naturally.

TL;DR: Blending is neither superior or inferior to chewing.


Nutritional Tunnel Vision

Sadly, there is a LOT of alarmism in the natural health movement – especially in the natural health blogosphere.

I frequently read alarmist, “click bait” headlines suggest that certain healthy foods are actually destroying our health. Low-carb proponents like to lump healthy carbs, like fruit, in with bad carbs.

One of the biggest problems with the natural health movement is that people (both experts and those who follow them) are so focused on isolated nutrients or anti-nutrients that the big picture of health is missed.

Absolutely every food you eat has a downside – even the healthiest, organic and bio-dynamic food out there.

Every breath of air, every sip of water, every bite of food, has both good and bad things in it, and your body is well equipped to handle it all just fine.

Focusing on the oxalate content of leafy greens is silly. It’s as silly as avoiding bananas because they contain fructose, or avoiding kale because of glucosinolates, or avoiding breathing air because oxygen is toxic.

Yes, oxygen is toxic, but it’s not toxic in the amount found in the air at the Earth’s surface. And the oxalate content of edible leafy greens are not toxic in the amount found in normal portions you would put in a daily green smoothie.

I encourage you to cast off the nutrition-fear blinders and take a step back from the noise of conflicting opinions about health and nutrition. Focus on the big picture of health – whole foods, exercise, plenty of water, friendship, sunshine and spending as much time as you can doing what you love.

Therein lies the key to health, not to mention the peace of mind and serenity to enjoy what you eat without worrying about all the conflicting opinions that are out there about what you put in your body.

And you might suspect that I am motivated to defend green smoothies because I write a green smoothie blog. Fair enough, but look at the science (not just opinion).

Don’t just read articles written by holistic doctors. Compare what they write and say against what is discussed in peer-reviewed scientific journals.

But above all, don’t worry about isolated nutrients or supposedly toxic compounds in otherwise healthy fruits and vegetables, unless a diagnosed medical disorder warrants it.

An exposé about the health disaster of any fruit or vegetable (or generally considered healthy food, for that matter) is simply noise that only serves to distract you from the big picture of health.

So go ahead and raise a glass of green smoothie to your health. I’ve been doing it every day for almost five years now!

TL;DR: Enjoy your green smoothie and stop worrying about it!

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Magick Monday

Medical Disclaimer: The information on this website is not intended to be used as medical advice or to replace a one-on-one relationship with a qualified healthcare professional. The statements made on this website have not been evaluated by the Food and Drug Administration. Always work directly with a qualified medical professional before attempting to treat any illness or medical condition with diet and lifestyle, or when changing or discontinuing any prescription medications. Always check with your doctor before starting any new diet or fitness program.